/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.mapred;

import java.util.Comparator;

/**
 * Order {@link JobInProgress} objects by submit time and then by priority and finally hash code
 */
public class FifoJobComparator implements Comparator<JobInProgress> {
  static FifoJobComparator instance = new FifoJobComparator();
  public int compare(JobInProgress j1, JobInProgress j2) {
    int res = 0;
    if (j1.getStartTime() < j2.getStartTime()) {
      res = -1;
    } else {
      res = (j1.getStartTime() == j2.getStartTime() ? 0 : 1);
    }
    if (res == 0) {
      res = j1.getPriority().compareTo(j2.getPriority());
    }
    if (res == 0) {
      res = j1.hashCode() - j2.hashCode();
    }
    return res;
  }
  public static FifoJobComparator getInstance() {
    return instance;
  }
}

